InfoWorks Collection System (CS) with its embedded Geographic Information System (GIS) applications is an approach of one-dimensional hydrodynamic modeling tool that used to identify the causes of inundation. Sungai Merah residential area covered an area of 0.47 km2 in Sibu Town of Sarawak State, located within the Seduan River basin, which is a flood-prone area with relatively flat and typically low-lying floodplain. The simulated model, used for the integrated assessment of flood conditions in the study area; for risk-based design of flood protection measures and hence as a decision support tool for flood risk management. Additionally, flood mitigation in the study area is part of the Sibu Town urban water management system, which proposed 3.7 m high levee to be constructed along the Seduan River to protect the residential area from tidal impact. Tidal gates are also provided to overcome the internal drainage problems. The hydrodynamic modeling showed its capability in identifying the effectiveness of the levee for 2, 5, 10 and 20 years Average Recurrence Interval (ARI).

Sarawak is Malaysia's largest state located on the island of Borneo. Typically, Sarawak has a tropical climate with hot and humid throughout the year with an average temperature ranging from 23 °C to 32 °C. The climate is influenced by two monsoon winds, namely, the north-east monsoon from November to February and the south-east monsoon from April to September. Nevertheless, Sarawak encountered an average rainfall of 3,905 mm annually with total surface water runoff about 306 billion m. Sibu Town is located in the heart of Sarawak at a distance of 100 km north of the South China Sea (Figure 1) with its confluence of three major rivers, namely, the Rajang River, the Seduan River and the Igan River. Sibu Town is built on flat and soft soil-peat, ranges from 2-5 m amsl (Tang, 2009).

The study area surrounded by stormwater drain and perimeter drain of Sungai Merah (SM) residential area to the outlet of the Seduan River (Figure 1). SM catchment is relatively flat and typical of a low-lying floodplain. Due to rapid developments in SM catchment, the communities in the area had suffered land subsidence and seasonal flooding within the catchment. To minimize its runoff, the local authority Sibu Municipal Council (SMC) had carried out annual maintenance on drainages and upgrading of roads. For long-term flood mitigation measure, drainage and stormwater infrastructures had been proposed within the study area. Due to tide level from the Seduan River coincided with excessive rainfall, SM residential area likely impact flood flows. Hence, recent desktop study by Putuhena et al. (2010) had shown flood in SM residential area was caused by poor maintenance, severe inundation and water logging in the drainage system. Therefore, an investigation was conducted to understand the flood behaviors and effectiveness of the proposed hydraulic structure3.7 m high levee along the Seduan River. For this study, the approach served as a demonstration tool for the government and private agencies as well as SMs communities to uphold against future floods.

Soil And Water Sciences Journal, InfoWorks Collection System, Hydrodynamic Modeling, Geographic Information System Applications, Flood Risk Management, Sibu Municipal Council, Government Agencies, Open Canal Drainage System, Flood Modeling, Digital Terrain Model, Demonstration Tools, Stormwater Management Plan.